Reproducing system



May 23, 1933. YElDER 7 1,909,995

REPRODUC ING SYSTEM Filed April 23. 1930 Inuen Ur Harry 5.5[515512Patented May 23, 1933 UNITED STATES HARRY A. YEIDER, or GRAND RAPIDS,MICHIGAN,

INSTRUMENT WARE PAT-m"omen REPRODUCING- SYSTEM Application filed April23,

transmitting the same to a remote point.

. More specifically, the invention'relates to an improved circuitarrangement for caus-' ing sound waves to be translated into electricalwaves by means of a variable condenser of novel construction. In theem-, bodiment of my invention illustrated in the attached drawing I haveapplied my invention to a phonograph reproducer or pickup? device. A Inthis embodiment the vanable condenser of my invention is operated by theneedle of the phonograph and translates the mechanical vibrations orconvolutions of the record groove into corresponding electrical waves. V

' Among the features of my invention are the provision of an improvedtranslat ng and amplifying system for reproduclng sound; to provide anovel reproducing sys tem employing a variable condenser, to pro-. videa condenser pickup for phonographs which gives truer reproduction andgreater amplification due to the design. of the C11- cuit and to thefact that the moving parts are simpler, lighter and have exceptionallyfree movement.

The embodiment by means of which I have chosen to illustrate myinvention is shown-in the accompanying sheet of drawing in which 7 Fig.1 is a top view of .thetone arm of. a phonograph with certain partsthereof shown in section.

Fig. 2 is a view of the device of Fig. 1 taken from the bottom of Fig. 1and also having most of its parts shown in section.

Fig. 3 is an end view taken from the rightof Fig. 2 also having certainparts shown in section. V

Fig. 4. is a view taken from. the bottom of Fig. 3 to more clearly showthe arrangement of the parts. c

Fig. 5 is a circuit diagram showingthe 4 electrical connections andcircuit operation of the improved translating and amplifying system. YIt has become common practice since the the condenser.

1930. Serial No. 446,490." I

combination of radio receiving sets and phonographs to use: theso-called magnetic pickup fortranslating the mechanical vibrations ofthe needle into electrical waves for transmission to the I'loud speaker.Although such devices have been-fairly satisfactory I have found thatthepresent design of a variable condenser. pickup gives greater volume,truer tone, and less distor tion due to the lighter. moving parts.

Referring to the accompanying drawing,

figs. 1 and 2, I have shown at 1 the usual mounting for a Connectedthereto .and'rigid therewith is a thin metal tube 2 with its ends closedwith parts 3 and 4. each of which has a rubber bushing in a socket onits inner face. The stylus bar 5'is mounted at each end inthese bushings.6 and 7. The stylus holder 8 is secured to bar 5.0n an angle as shownpreferably by solder or a rigid joint of any type and extends downthrough? a large opening in the lower side of tube 2 as shown. A springand plunger needleiejec tor is mounted inside the stylus"h0lder.- theopposite end of the stylus bar 5 is another hole threaded to receivea'stud 9 which also projects out through a large opening in tube 2 downinside the dome mounting 1. The lower end of stud; 9 is reduced to asmall diameter and mounted thereon by aset screw 10 is acopper plate 11which has an enlarged upper portion containing a hole which fits overthe reduced end of stud 9, and which-isadjustably' held by set screw 10.Around the tube 2 and inside the dome mounting 1 is a 'U-shaped metallicbracket 12 inside of which isa thin metal retaining member 13,'alsoU-shaped and fitting tightly around-'thetube 2. Both brackets 12 and 13are secured together atthe top and also secured to the' tube 2'byphonograph tone arm.

7 ASSIGNOR ro AU'roMArIoMUs cAI. V COMPANY, or GRAND RAPIDS, MICHIGAN, ACORPORATION or nEL soldering or other means. The bracket 13 at itslowerends has extending arms ltand 15 which are bent outward and fit snuglyaround bracket 12 to hold it rigid, lugs 14 and 15 are also soldered orsecured to brack-v et'.12. .Bracket l4; has an extending tip 14 whichmay be used. as one terminal of I In one of the, lower ends parts ofbracket 12 (Figs. 3 and 4) is an insulating bushing 16 through whichextends a stud 17 which is welded to and supports a copper plate .18adjacent the plate 11. Between the plates 11 and 18 is a dielectric ofpaper, mica, or other insulating material shown at 19 and the plate 18is held clamped close to the dielectric by nuts 20 and 21 which also.hold a, copper terminal 22 in contact WithJstud 17. and therethrough toplate 18to provide a second terminal for the condenser. other arm ofbracket 12 is a stud '23'threaded into a hole in the bracket and havingwation and are shown here only as an adjunct.

to my present invention.

As is usual in such devices, the tone arm is mounted as indicated inFig. 2 by a universal joint to a platform such as'26, only of which areshown. Thus it will be seen that when the stylus 8 is placed on a recordthe sidewisemovement thereof when following the curves or convolutionsof a.

groovein a record will be communicated 5 through the stylus bar 5 to thestudy 9 and. thence to. the copper plate 11. The corre sponding sidewisevibrations of plate 11, will causevariatious of the capacity of thecondenser formed by plates 11 and 18 and the dielectric 19 by varyingthe. distance between the plates.

Referring now to shown in Fig. 5, I will explain the connection andfunction of the variable condenser shown in Figs. 1 1. At V I have'showna welllmown, type of 3-element vacuum tube having filament, grid, andplate. 'The tube may be the direct or alternating current type of tubeas desired and will of-course 3 have the usual connections to a batteryfor energizing. the filament, a connection to battery through resistance27 for biasing the, grid, ,andthe usual B battery connections to theplate, theoutput to loudspeaker or the like may-be taken through theprimary of a transformer such as shown at 28 if desired. As any type oftube may be used, ;I have not shown the A, .B, and 0 batteries. but onlyindicated the same by lettersr 1 Across the input'of thetubeI connect .asource of high potential direct current ofa value which maybeapproximately 500 volts as shown; 1 The positive sidejof the directcurrent source is connected through'resist- In the lower end of ,the.

the circuit diagram.

ances 29 and 30 and through a series con denser 31 of fairly highcapacity to the grid of tube V. The negative side of the 500 V source isconnected to the midpoint of a resistance 32 bridged across the filamentof the tube. A condenser 33 is bridged from the negative side of thehigh potential source to the midpoint between resistances 29 and 30 andthese two resistances and 30 and condenser: 33 actv as a smoother forthehigh' potential direct current source tov prevent variations .orundulations in the voltage thereof from reaching the tube. At a pointbetween the resistance 30 and condenser 31 the variable condenser 34,which comprises plates 11 and 18, has one of -it'splates connected andthe other plate isconnected tothe negative'side. of the, highpotentialbattery.

It is well understood that variation s in theimpressed'electromotiveforce on the grid of the vacuum tube causevariations in the flow. of electronsbetween filament and plate andproduce amplified changes in the current flowing in theoutput circuit ofthe tube. It will be, seen, therefore, that as the needle or stylus 8causes variations in the capacityv of condenser 34 by compressingplates. 11 and18,that thesaid variations in capacity ofcondenser 84.will cause Variations in the charge carried by the condenser 31 andtherefore cause a correspondingly varying voltage to be set .up in thegrid circuit of the tubeV. As long as condenser 34 is not varied thetube is inactive and the condensers 34. and 31-stan'd charged. The useof the high voltage and theconnection of the variable. condenser84 asshown causes sharp and rapid changes-in the grid potential andcorrespondingly strong and rapid'current changes in the plate circuitresulting from changes in capacity of'condenser 34..

The action of the circuit will be understoodby those skilled in the art,and it will be seen that as the capacity of condenser 3 1 is increasedby plates 11 and 18 coming close together, it will cause a lowering ofthe potential on grid of tube V; Alsoas plates 11 and 18 are drawn apartand the capacity is decreased, a current will flow through condenser31'and in the opposite direction over and above traced circuit, to causeconsequent increases of the; voltage onthe grid.

'It Wlll be seen, therefore, that I have provided a very eflicient :andsimple type of pickup and that very slight movement. of. the plate ll ofcondenser 34 produces corresponding amplified fluctuations in the platecircuit of the amplifier. As previously suggested, although theinvention is illustrated as a phonograph pickup,it should be understoodthat the'plate 11 of condenser 34 may, if desired, be vibrated directlyby adiaphragm or in any other desired inanher to reproduce sound, andalso that various changes may be made in the detailed arrangementillustrated without departing from the spirit of the invention.

Having fully described and ascertained the features and aspects of myinvention, what I consider to be new and desire to have protected byLetters Patent will be pointed out'in the appended claims.

What is claimed is:

1. In a device of the class described, a pickup supporting arm having arod'yieldingly supported therein, a stylus mounted on one end of saidrod, a plate mounted on the opposite end of said rod, another plateadjacent said first plate and a dielectric between the plates forming acondenser,

the vibrations of the stylus causing corresponding vibrations of thefirst plate through the medium of said rod and consequent variations inthe capacity of the condenser.

2. In a device of the class described, a variable condenser comprising astationary plate and a movable plate, a dielectric separating saidplates, a rod supporting said movable plate on one end thereof, a stylusmounted on the opposite end of said rod and extending sidewise therefromand ar-' ranged to communicate its vibrations to the condenser byrotating said rod on its own axis to vary the capacity of saidcondenser, means for adjusting the normal capacity of the condenser byspacing the movable plate from the stationary plate, and meansresponsive to the variations in capacity of the condenser for producingcorresponding electrical variations in a circuit. 7

3. In a device of the class described, a pickup supporting arm pivotallymo-rnted at one end, the other end being rotatable abouirsaid pivotedend, a condenser mounted on the pivoted end of said arm, a stylusmounted on the movable end of said arm and having means for producingvariations in the capacity of said condenser, and means responsive tothe capacity variations of the condenser to produce correspondingelectrical variations in a circuit.

In witness whereof, I hereunto subscribe my name this 17th day of April,A. D. 1930.

HARRY A. YEIDER.

